Eastern narrowmouth toad description

The colour of the smooth skin of the eastern narrowmouth toad (Gastrophryne carolinensis) is highly variable within and between populations, and may be grey, brown, brown-yellow or reddish (3). Some individuals may have a wide, wavy, dark band that runs along the middle of the back (2)(3). The underside of this amphibian is darkly coloured, patterned with lighter specks (2) and unlike the upper surface, may have a slightly rough appearance (3). The body is pear-shaped (3) and the head is small (2) with a sharply pointed snout (2)(3) and a red oval on either side, which are located where the hearing organs are internally positioned (2). The toes are not webbed (2)(3) and there are horn-like lumps on the rear feet, which are used for digging (2).

The female eastern narrowmouth toad is generally larger than the male, although its physical appearance is similar (2)(4). During the breeding season, it is easy to distinguish the sexes from each other, as the male has a darkly coloured vocal sac on its throat, which is especially prevalent when it calls (2) and it also develops enlarged tubercles on its chin and jaw (4). When in the larval tadpole stage of life, this species is mostly black (2)(3), occasionally with a white stripe along each side of the tail. When viewed from above, the body of the tadpole is rather square, but with rounded corners. The body is relatively flat when viewed from the side (3).

The mating call of the eastern narrowmouth toad is often compared to a bleating lamb (2)(3)(4), although it is more nasal and has a slightly higher pitch (2).

Related species

Eastern narrowmouth toad biology

As a method of defence against predation, the eastern narrowmouth toad secretes mucous from glands in its skin (2)(3)(4), which is toxic to other amphibians, and causes a burning sensation in the eyes, mouth and throat of humans (4). This also prevents attacks from ants and termites, which are the main components of this species’ diet (2)(4). Small beetles and other arthropods are also taken, but to a lesser extent (2)(3)(4). In its larval phase, the eastern narrowmouth toad tadpole feeds by filtering organisms and organic matter out of the water column (2)(3)(4).

Eastern narrowmouth toad breeding usually occurs during warm, rainy weather between late spring and early autumn (3). The male usually calls during the night along the edge of a breeding pool or hidden among vegetation in the water (2)(3)(4). A non-territorial species, males may be found calling for a mate as close as two centimetres from each other (4). Once the male has attracted a female, it secretes a glue-like substance, which acts as an adhesive to hold the pair together while they mate (2)(4). The female may release over 1,000 eggs, which are laid in groups of between 10 and 100 (3). The eggs float on the surface of the water in a thin film and hatch within a few days (3)(2). Over the next ten weeks (2)(3)(4), the tadpoles grow steadily, until they reach the end of the development period when metamorphosis occurs very rapidly (4). The timing of the metamorphosis is dependent on where the population is, with those in Georgia metamorphosing between mid-June and September and between August and September in Virginia (4). The male and female can both reach sexual maturity after one year of life, although it may take up to two years for some females (2).

Eastern narrowmouth toad range

The eastern narrowmouth toad is endemic to the United States, where it is found from Maryland in the east to southeast Kansas in the west. Populations of this species are found as far south as the Florida Keys and eastern Texas (1)(4).

The eastern narrowmouth toad has also been introduced to Grand Cayman Island and The Bahamas, where there are now established populations (1).

Species with a similar range

Eastern narrowmouth toad habitat

The eastern narrowmouth toad spends much of its life underground in terrestrial habitats (2)(3), including prairies(4) and forests (2)(3). They are accomplished burrowers (2) and build underground tunnels in a wide variety of soil types (3), although sandy or loamy soils are preferred (2). When this species comes to the surface, it usually hides in moist areas underneath leaf litter, logs or rocks (2)(3)(4). It is also found around residential areas and other modified habitats (1)(4).

The eastern narrowmouth toad reproduces in various temporary aquatic habitats, such as ponds, flooded roadside ditches (1)(2) and rain puddles (1). They are able to tolerate brackish water and some populations live on barrier islands and other saltwater habitats (4).

Eastern narrowmouth toad status

Eastern narrowmouth toad threats

The biggest threat to the eastern narrowmouth toad is habitat loss, which is occurring in various areas throughout its range due to urbanisation and road construction (4). Developments have fragmented many parts of this species’ habitat, which can lead to genetic problems within the population, such as inbreeding depression(3)(4). Direct mortality is caused by construction processes in natural habitats, as well as by individuals being hit by moving vehicles when attempting to cross roads (3).

Authentication

Glossary

A major grouping of animals that includes crustaceans, insects and arachnids. All arthropods have paired jointed limbs and a hard external skeleton (exoskeleton).

Brackish

Slightly salty water, usually a mixture of salt and freshwater, such as that found in estuaries.

Endemic

A species or taxonomic group that is only found in one particular country or geographic area.

Gland

An organ that makes and secretes substances used by the body.

Inbreeding depression

The reduction in viability, birth weight, and fertility that occurs in a population after one or more generations of inbreeding (interbreeding among close relatives).

Larval

Of or relating to the immature stage in an animal’s lifecycle, after it hatches from an egg and before it changes into the adult form. Larvae are typically very different in appearance to adults; they are able to feed and move around but are usually unable to reproduce.

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